This invention relates to a novel electric box assembly for mounting electrical components, such as receptacles and switches, and particularly to an improved plastic electric box assembly which is especially adapted for use in wiring systems for mobile homes and the like. The electric box assembly of the present invention has particular utility in a ceiling panel, although it will be evident from the following description that it may also be used in a wall panel, or the like.
A large variety of electrical boxes for receiving electrical components have been developed and are available on the market. Some of these are metallic, and others are of plastic and of glass fiber reinforced plastic materials. Most of the boxes currently available require the use of extraneous fasteners, such as nails, screws, and the like, to secure them to a panel, such as a wall panel or ceiling panel, or to a panel supporting frame in order to comply with existing building codes.
The properties of wall and ceiling panels in mobile homes have been found to vary significantly. Wall panels are usually formed from materials that are relatively thin, rigid and strong, while ceiling panels are conventionally formed from thicker materials that are relatively soft and weak, such as sound deadening materials. Most ceiling box installations require reinforcing or load spreading members above the ceiling panels to spread the weight of the fixtures that are hung from the boxes, and/or to provide a suitable anchor for screws used to hold the boxes place and support the fixtures. The total thickness of panels with reinforcing members, where used, has been found to vary from 0.140 inches to 1.50 inches.
Where a ceiling panel reinforcing member is required, it is necessary that it be fastened to the ceiling framework, or manually held from above the ceiling when installing the electric box. Such reinforcing members are commonly referred to as "donuts," and consist of a relatively rigid member, such as a piece of plywood, having a hole therein disposed in alignment with a hole in the ceiling panel. To secure such a member in place, some manual installation work must be done from above the ceiling panel prior to, or during, installation of the electric box. Usually a workman must hold the donut in place above the panel while another workman drives the screws, which hold the box in place, through the panel into the donut. Likewise, when an electric box is secured to a wall panel by means of screws and a reinforcing member is required, two workmen are required for the installation, one to hold the donut behind the panel, and the other to insert the box and drive the screws from the front of the panel.
Commonly assigned U.S. Pat. No. 3,848,764 to Salg discloses an electric box that can be affixed to a panel without the use of extraneous fasteners. A panel securing assembly is employed which is preferably integrally formed with the electric box structure and includes at least two spaced stop members and cooperable deflectable resilient spring fingers. The spring fingers deflect inwardly when the box structure is inserted in an opening in the panel, and then return to their outwardly sprung position so that the panel is positioned between the stop members and spring fingers. The electric box is limited to panel installations where the panels are made of a relatively dense and strong material and do not vary greatly in thickness.
The electric box disclosed in commonly assigned U.S. Pat. No. 3,891,113 to Salg is an improvement over the electrical box disclosed in U.S. Pat. No. 3,848,764 in that the sidewall of the box is continuous and flexes inwardly when the box is inserted into a panel opening. The rigidity of this electric box prevents it from being used in most ceiling panels because most ceiling materials are soft and weak and do not have sufficient stiffness or rigidity for accepting this type of "snap-in" type of electic box.
And, because of their structural configuration, the electric boxes disclosed in the above-mentioned commonly assigned patents are more or less limited to a panel of given thickness, which is satisfactory for wall panels that are generally uniform in thickness throughout the industry, but which is not completely satisfactory for ceiling panels which vary greatly in thickness.
Thus, in spite of the improvements provided by the electric boxes disclosed in the aforementioned patents, a need remains in connection with electric boxes that can be readily installed in weak, soft panels of varying thicknesses without the use of extraneous fasteners, and/or reinforcing members.